Field of the Invention
The present invention relates to a piezoelectric ceramic containing neither lead nor alkali metals. More particularly, the present invention relates to a piezoelectric ceramic compatibly representing both an excellent piezoelectric constant and an excellent mechanical quality factor at low temperatures. The present invention also relates to a piezoelectric element, a laminated piezoelectric element, a liquid ejection head, a liquid ejection device, an ultrasonic motor, an optical instrument, a vibration device, a dust removal device, an image pickup device, an electronic instrument and a piezoelectric device realized by using such a piezoelectric ceramic as well as to a piezoelectric ceramic manufacturing method.
Description of the Related Art
Perovskite type oxides having a composition expressed by ABO3 such as lead zirconate titanate (to be referred to as “PZT” hereinafter) are popularly known materials of piezoelectric ceramics. However, since PZT contains lead as site A element, apprehensions have been expressed for its adverse effects on the environment of this planet. For this reason, there have been proposed piezoelectric ceramics realized by using a perovskite type oxide that does not contain lead.
Barium titanate is known as a piezoelectric ceramic including a perovskite type oxide that does not contain lead. Japanese Patent No. 5,344,456 discloses a piezoelectric ceramic obtained by partly replacing the barium atoms at the sites thereof in molecules of barium titanate by calcium atoms and also partly replacing the titanium atoms at the sites thereof by zirconium atoms in order to improve the piezoelectric characteristics of barium titanate at and near the room temperature. However, a piezoelectric ceramic disclosed in Japanese Patent No. 5,344,456 represents a low mechanical quality factor and is poorly durable at high temperatures and hence it is not suited to be used in resonance devices.
Japanese Patent No. 5,217,997 discloses a piezoelectric ceramic obtained by partly replacing the barium atoms at the sites thereof in molecules of barium titanate by calcium atoms and adding manganese, iron or copper. Japanese Patent NO. 5,217,997 describes that the ceramic has an excellent mechanical quality factor at and near the room temperature. However, the mechanical quality factor of the piezoelectric ceramic disclosed in Japanese Patent No. 5,217,997 falls at low temperatures (not higher than 0° C.) and hence the piezoelectric ceramic is not suited to be used in resonance devices.
The present invention has been made to overcome the above-identified problems of the prior art. This invention provides a piezoelectric ceramic compatibly representing both an excellent piezoelectric constant and an excellent mechanical quality factor particularly at low temperatures by controlling the composition of crystal grain boundaries and also the crystal structure thereof.
The present invention also provides a piezoelectric element, a laminated piezoelectric element, a liquid ejection head, a liquid ejection device, an ultrasonic motor, an optical instrument, a vibration device, a dust removal device, an image pickup device, an electronic instrument and a piezoelectric device realized by using such a piezoelectric ceramic along with a piezoelectric ceramic manufacturing method.